Stoichiometry: Chapter 9

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This is the 1/2 half of the notes for Chapter 9 over Reaction Stoichiometry.

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Stoichiometry: Chapter 9

  1. 1. STOICHIOMETRY Chapter 9 Modern Chemistry S.Martinez – Spring 2011
  2. 2. <ul><li>Ch 9 Vocab – 8 words </li></ul><ul><li>Lab # 6 & Lab # 7 Reports are due </li></ul>
  3. 3. Intro to Stoichiometry <ul><li>Composition vs Reaction Stoichiometry </li></ul><ul><ul><li>Comp – mass relationship of elements in compounds </li></ul></ul><ul><ul><li>Reaction – mass relationship between reactants and products in chem rxn </li></ul></ul>
  4. 4. 4 Types of Reaction-Stoichiometry Problems <ul><li>Type 1: </li></ul><ul><ul><li>Given and unknown amounts are in moles </li></ul></ul><ul><li>Type 2: </li></ul><ul><ul><li>Given amt in moles and unknown needs to be in grams </li></ul></ul><ul><li>Type 3: </li></ul><ul><ul><li>Given amt in grams and unknown needs to be in moles </li></ul></ul><ul><li>Type 4: </li></ul><ul><ul><li>Given and unknown amts are in grams </li></ul></ul>
  5. 5. Mole Ratio <ul><li>Any of the reaction problems can be solved using ratios. </li></ul><ul><li>Mole ratio is derived from the coefficients in a balanced chemical equation. </li></ul><ul><li>Ex: Decomposition of aluminum oxide by electrolysis </li></ul><ul><ul><li>2Al 2 O 3  4Al + 3O 2 </li></ul></ul>
  6. 6. <ul><li>Ex: Decomposition of aluminum oxide by electrolysis </li></ul><ul><ul><li>Determine the amount of Aluminum that can be produced from 13.0 mol of aluminum oxide. </li></ul></ul>Equations <ul><ul><li>2Al 2 O 3  </li></ul></ul>4Al + 3O 2 Moles 2 moles 4 moles 3 moles Molar mass Grams
  7. 7. Molar Mass as a Ratio <ul><li>Using the same problem, calculate the number of grams of aluminum equivalent to 26.0 moles of aluminum. </li></ul>
  8. 8. Section 9.2 <ul><li>Chemical Equations help make predictions about chemical reactions without having to run the reactions in the laboratory. </li></ul><ul><li>All of the reaction stoichiometric problems are theoretical, meaning we are assuming ideal conditions in which all reactants are converted into products. </li></ul><ul><li>Theoretical stoichiometric calculations show the maximum amt of product that could be obtained. </li></ul>
  9. 9. Problem Type #1 <ul><li>+ </li></ul>Amt of given substance in mol Amt of unknown substance in mol
  10. 10. <ul><li>In a spacecraft, the carbon dioxide exhaled by astronauts can be removed by its reaction with lithium hydroxide, LiOH. </li></ul><ul><li>How many moles of lithium hydroxide are required to react with 20 mol of carbon dioxide, the average amount exhaled by a person each day? </li></ul><ul><li>CO 2 + 2 LiOH  Li 2 CO 3 + H 2 O </li></ul>
  11. 11. <ul><li>Answer: 40 moles of LiOH </li></ul>
  12. 12. <ul><li>Ammonia is widely used as a fertilizer and in many household cleaners. How many moles of ammonia, NH 3 , are produced when 6 mol of hydrogen gas react with an excess of nitrogen gas? </li></ul>
  13. 13. <ul><li>Answer: 4 moles of Ammonia </li></ul>
  14. 14. <ul><li>The decomposition of potassium chlorate is used as a source of oxygen in the laboratory. How many moles of potassium chlorate are needed to produce 15 mol of oxygen? </li></ul>
  15. 15. <ul><li>Answer: 10 mol KClO 3 </li></ul>
  16. 16. <ul><li>The elements Lithium and oxygen react explosively to form lithium oxide. How many moles of lithium oxide will form if 2 mol of lithium react? (synthesis rxn) </li></ul>
  17. 17. <ul><li>Answer: 1 mole of Lithium Oxide </li></ul>
  18. 18. <ul><li>The disinfectenct hydrogen peroxide, H 2 O 2 , decomposes to form water and oxygen gas. How many moles of oxygen will result from the decomposition of 5 mol of hydrogen peroxide? </li></ul>
  19. 19. <ul><li>Answer: 2.5 mol of oxygen </li></ul>
  20. 20. Problem Type 2 <ul><li>Starting in moles ending in grams </li></ul><ul><li>Moles to moles to grams </li></ul>
  21. 21. <ul><li>In photosynthesis, plants use energy from the sun to produce glucose, C 6 H 12 O 6 , and oxygen from the reaction of carbon dioxide and water . What mass, in grams, of glucose is produced when 3.00 mol of water react with carbon dioxide? </li></ul>
  22. 23. <ul><li>In photosynthesis, plants use energy from the sun to produce glucose, C 6 H 12 O 6 , and oxygen from the reaction of carbon dioxide and water . What mass, in grams, of glucose is produced when 3.00 mol of water react with carbon dioxide? </li></ul><ul><li>CO 2 + H 2 O  C 6 H 12 O 6 + O 2 </li></ul>
  23. 24. <ul><li>In photosynthesis, plants use energy from the sun to produce glucose, C 6 H 12 O 6 , and oxygen from the reaction of carbon dioxide and water . What mass, in grams, of glucose is produced when 3.00 mol of water react with carbon dioxide? </li></ul><ul><li>CO 2 + H 2 O  C 6 H 12 O 6 + O 2 </li></ul><ul><li>6 CO 2 + 6 H 2 O  1 C 6 H 12 O 6 + 6 O 2 </li></ul>
  24. 25. <ul><li>In photosynthesis, plants use energy from the sun to produce glucose, C 6 H 12 O 6 , and oxygen from the reaction of carbon dioxide and water . What mass, in grams , of glucose is produced when 3.00 mol of water react with carbon dioxide? </li></ul><ul><li>CO 2 + H 2 O  C 6 H 12 O 6 + O 2 </li></ul><ul><li>6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 </li></ul><ul><li>3 mol ? grams </li></ul>
  25. 26. <ul><li>6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 </li></ul><ul><li>3.00 mol of H 2 0 x (1 mol glucose/6 mol of water) = 0.500 mol of glucose </li></ul><ul><li>0.500 mol of glucose x (180.18 grams/mol) </li></ul><ul><li>= 90.09 grams of glucose </li></ul><ul><li>C – (6 x 12.01) = 72.06 </li></ul><ul><li>H – (12 x 1.01) = 12.12 </li></ul><ul><li>O – ( 6 x 16.00) = 96.00 </li></ul><ul><li>Total molar mass = 180.18 g/mol </li></ul>
  26. 27. <ul><li>What mass of carbon dioxide, in grams, is needed to react with 3.00 mol of water in the above photosynthetic reaction? </li></ul><ul><li>6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 </li></ul>
  27. 28. 6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2
  28. 29. <ul><li>6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 </li></ul><ul><li>3.00 mol of water x ( 6 mol of water/6 mol of CO 2 ) = 3.00 mol of CO 2 </li></ul><ul><li>3.00 mol of CO 2 x (44.01 grams/mole) = 132. grams of carbon dioxide </li></ul><ul><li>C – (1 x 12.01) = 12.01 </li></ul><ul><li>O – (2 x 16.00) = 32.00 </li></ul><ul><li>Molar mass = 44.01 grams/mole </li></ul>
  29. 30. <ul><li>When magnesium burns in the air, it combines with oxygen to form magnesium oxide. What mass, in grams, of magnesium oxide is produced from 2.00 mol of magnesium? </li></ul>
  30. 31. <ul><li>When magnesium burns in the air, it combines with oxygen to form magnesium oxide. What mass, in grams, of magnesium oxide is produced from 2.00 mol of magnesium? </li></ul><ul><li>2 Mg + O 2  2 MgO </li></ul>
  31. 32. 2 Mg + O 2  2 MgO
  32. 33. <ul><li>When magnesium burns in the air, it combines with oxygen to form magnesium oxide. What mass, in grams, of magnesium oxide is produced from 2.00 mol of magnesium? </li></ul><ul><li>2 Mg + O 2  2 MgO </li></ul>
  33. 34. <ul><li>2 Mg + O 2  2 MgO </li></ul><ul><li>2.00 mol Mg x (2 mol of MgO/2 mol of Mg) = 2.00 mol MgO </li></ul><ul><li>2.00 mol MgO x (40.31 grams/mole) = 80.6 grams </li></ul>
  34. 35. <ul><li>What mass in grams of oxygen combines with 2.00 mol of magnesium in this same reaction? </li></ul><ul><li>2 Mg + O 2  2 MgO </li></ul>
  35. 36. <ul><li>What mass of glucose, C 6 H 12 O 6 (molar mass 180.18 g/mol, solved from a previous problem) can be produced from a photosynthesis reaction that occurs using 10 mol CO 2 ? </li></ul><ul><li>6 CO 2 + 6 H 2 O  C 6 H 12 O 6 + 6 O 2 </li></ul>
  36. 37. <ul><li>Answer: 300 grams of glucose </li></ul>
  37. 38. <ul><li>When sodium azide is activated in an automobile airbag, nitrogen gas and sodium are produced according to the equation: </li></ul><ul><li>NaN 3  Na + N 2 </li></ul><ul><li>If 0.500 mol of NaN 3 react, what mass in grams of Nitrogen would result? </li></ul>
  38. 39. <ul><li>Answer: 21.0 grams of Nitrogen </li></ul>
  39. 40. <ul><li>Carborundum, SiC, is a hard substance made by combining silicon dioxide with coke(C) as follows: </li></ul><ul><li>SiO 2 + 3C  SiC + 2CO </li></ul><ul><li>What mass in grams of SiC is formed from the complete reaction of 2.00 mol of carbon? </li></ul>
  40. 41. <ul><li>Answer: 26.7 grams of SiC </li></ul>
  41. 42. <ul><li>Coal can be converted to methane gas by a process called coal gasification. The equation for the reaction is the following: </li></ul><ul><li>2C + 2H 2 O  CH 4 + CO 2 </li></ul><ul><li>What mass in grams of carbon is required to react with water to form 1.00 mol of CH 4 ? </li></ul>
  42. 43. <ul><li>Answer: 24.0 grams C </li></ul>
  43. 44. Problem Type 3 <ul><li>Starting in grams ending in moles </li></ul><ul><li>Grams to moles to moles </li></ul>
  44. 45. <ul><li>The 1 st step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia. </li></ul><ul><li>NH 3 + O 2  NO + H 2 O </li></ul><ul><li>The reaction is run using 824 g of ammonia and excess oxygen. </li></ul><ul><li>How many moles of nitrogen monoxide are formed? </li></ul><ul><li>How many moles of water are formed? </li></ul>
  45. 46. <ul><li>4 NH 3 + 5 O 2  4 NO + 6 H 2 O </li></ul><ul><li>The reaction is run using 824 g of ammonia and excess oxygen. </li></ul><ul><li>How many moles of nitrogen monoxide are formed? </li></ul><ul><li>How many moles of water are formed? </li></ul>
  46. 47. <ul><li>48.3 mol NO </li></ul><ul><li>72.5 mol of water </li></ul>
  47. 49. Problem Type 4 <ul><li>Starting in grams ending in grams </li></ul><ul><li>Grams of given to moles of given to moles of unknown to grams of unknown </li></ul>
  48. 50. <ul><li>Tin (II) fluoride, SnF 2 , is used in some toothpastes. It is made by the reaction of tin with hydrogen fluoride according to the following equation. </li></ul><ul><li>Sn + 2HF  SnF 2 + H 2 </li></ul><ul><li>How many grams of SnF 2 are produced from the rxn of 30.00 g of HF with Sn? </li></ul>
  49. 51. Sn + 2HF  SnF 2 + H 2 Sn 2HF SnF 2 H 2 Moles Given Molar mass Moles calc. Mass calc.
  50. 52. <ul><li>117.5 g SnF 2 </li></ul>
  51. 53. <ul><li>Laughing gas (dinitrogen monoxide) is sometimes used as an anesthetic in dentistry. It is produced when ammonium nitrate is decomposed according to the following rxn. </li></ul><ul><li>NH 4 NO 3  N 2 O + H 2 O </li></ul><ul><li>If 360 g of ammonium nitrate are decomposed how many grams of dinitrogen monoxide will be formed? </li></ul>

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